Sorry I don't have any experience with Progressive either, other than the annoying ad. Must be good advertising if it makes you remember iot though. I can however also recommend Coles as well.
We too have one of our cars with Coles who were $250 cheaper than our previous insurer (but interestingly the same price on the other car). They also threw in 12 months road side assist, the monthly petrol vouchers and guaranteed the price (as long as your circumstances don't change) for 2 years.
The doomsayers often say "there a reason they are cheap" and "wait until you have to make a claim" etc but I recently had a minor bingle when I was hit from behind in traffic. Coles could not have been better, one phone call of about 10 minutes sorted it out, all I had to do was give then the other parties details and choose where I wanted to get the car repaired (i.e. near home or work).
I rang on a Friday and took the car in for a quote to a place that suited me on Saturday morning. I got a phone call back on Monday morning asking if I had been able to get a quote. Everything was approved a couple of days later with a phone call saying just book it in when you are ready. The repairer then called to ask when suited me and even went out of their way to repair the car when I was away with work so I wasn't inconvenienced. The car was ready including a valet when I got back from my trip. Interestingly, the repairer had just switched his car insurance to Coles as they were great to deal with from his side too. Based upon this experience when the other car comes up for renewal it will be getting insured by Coles too.